Insulative substrates for electrical circuit devices typically include through holes which are "printed" through with conductive material to make an electrical connection from one side of the substrate to the other. The prior art technique for accomplishing of the through holes involves the use of a vacuum fixture which creates sufficient vacuum to hold the substrate in place while, at the same time, pulling air through the holes in the substrate as a conductive fluid is spread across the top surface of the substrate with the use of a squeegee.
The results of the through hole printing process briefly described immediately above have thus far been characterized by extreme non-uniformity due, in large part, to the inherent variations in the squeegee deposition process from one side of the substrate to the other, the variation in vacuum pressure during the deposition process as well as a similar variation from one substrate to the other and in the relative lack of sophistication in the deposition equipment; i.e., the equipment is technically oriented toward achieving the printing function and provides virtually no information on the relative qualities of the finished product from one to the other.